Reactivity Studies of a Zirconium Methylidene Complex: Group Transfer and Methylenation Reactions
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- 作者：Takashi Kurogi ; Masahiro Kamitani ; Brian C. Manor ; Patrick J. Carroll ; Daniel J. Mindiola
- 刊名：Organometallics
- 出版年：2017
- 出版时间：January 9, 2017
- 年：2017
- 卷：36
- 期：1
- 页码：74-79
- 全文大小：384K
- ISSN：1520-6041
文摘
The zirconium methylidene complex (PNP)Zr═CH2(OAr) (1; PNP = N[2-PiPr2-4-methylphenyl]2–, Ar = 2,6-iPr2C6H3), prepared from photolysis of (PNP)Zr(CH3)2(OAr), can engage in incomplete and complete methylidene group transfer reactions with CO, CDCl3, cyclododecanone, and benzophenone. When CO was treated with 1, methylenation occurred via the putative metalloketene adduct [(PNP)Zr(OCCH2)(OAr)], which ultimately afforded the C–C coupled enolate dimer [(PNP)Zr(OAr)]2(OCH2C═CCH2O) (2). Addition of CDCl3 to 1 rapidly resulted in formation of (PNP)ZrCl2(OAr) (3) along with liberation of d1-vinyl chloride, H2C═CDCl. Complex 3 could be readily prepared independently from (PNP)ZrCl3 and 1 equiv of NaOAr. Wittig reactivity was observed between 1 and cyclododecanone to afford methylenecyclododecane. Similarly, treating 1 with the ketone OCPh2 resulted in methylenation of the ortho position followed by tautomerization to produce the chelated alkyloxide complex (PNP)Zr(OAr)[OCHPh(C6H4)CH2] (4). In addition to the isolation of 4, complex 1 also engages in a cross-metathesis reaction involving the methylidene and ketone oxygen of benzophenone, as well as in olefin metathesis involving the formed olefin H2C═CPh2. Complexes 2–4 have been fully characterized, including solid-state structural analysis, and proposed mechanisms for the formation of species such as 2–4 are presented and discussed.